Illumination systems incorporating polarizing beam splitters (PBSs) are used to form images on viewing screens, such as projection displays. A typical display image incorporates an illumination source that is arranged so that light rays from the illumination source reflect off of an image-forming device (i.e., an imager) that contains the desired image to be projected. The system folds the light rays such that the light rays from the illumination source and the light rays of the projected image share the same physical space between a PBS and the imager. The PBS separates the incoming illumination light from the polarization-rotated light from the imager. Due to new demands on PBSs, in part due to their new uses in applications such as, e.g., three-dimensional projection and imaging, a number of new issues have arisen. The present application provides articles that address such issues.